As the fire spread through Ross Compton’s $400,000 home, the Middletown, Ohio, man knew he had to get out, but first he had to grab a few things.

Fifteen things, in fact, investigators determined.

He packed some of his clothes and other belongings in a suitcase. He put the stuff that wouldn’t fit in other bags. He grabbed his computer. He made sure to pick up the charger for his medical device. Then, he told dispatchers, he used his cane to break a window and hurl the bags out. After that, he says, he rushed out of the burning house.

It seemed like a lot of work for someone escaping a burning house — especially a man who needed a pacemaker and an external heart pump to survive.

There were other suspicious signs. Spaulding, who was on his way to work when he was diverted to the fire, noticed signs that the blaze had started in several locations. And as the smell of smoke receded, Spaulding could smell gasoline.

Weeks later, as investigators mulled how to make an arson charge stick, they realized that they had a way of corroborating just how much scrambling Compton was doing during the fire: His pacemaker was tracking every beat of his heart.

“We’d be able to see did he exceed his threshold limit,” Spaulding told The Washington Post. “Or did his pulse drop below a certain rate. It won’t say what you’re doing, obviously, but it would help corroborate his story. It was much more informative than we thought.”

It disproved Compton’s story instead, Spaulding said.

After investigators were granted a search warrant, a technician collected data from Compton’s heart during a noninvasive procedure. “All he had to give us was his time,” Spaulding said.

Now, Compton is charged with aggravated arson and insurance fraud in the Sept. 19 fire. A grand jury indicted him last month after a doctor testified that he couldn’t have done the things he claimed during the fire.

A cardiologist who reviewed the medical data for the investigation concluded that “it is highly improbable Mr. Compton would have been able to collect, pack and remove the number of items from the house, exit his bedroom window and carry numerous large and heavy items to the front of his residence during the short period of time he has indicated due to his medical conditions,” according to court documents obtained by the Middletown Journal-News.